Good morning!
So when we look at ratios like 10:18, we read them as "Ten out-of eighteen" and we can basically think of them like fractions. In this case, we can look at the ratio 10:18 to mean the same thing as 10/18.
Now let's look at the fraction 10/18. We can see that both numbers are divisible by 2. Therefore, we can have 10/18 = (10/2)/(18/2) = 5/9 and both fractions represent the same number/amount. We now have one equivalent ratio to 10:18, which is 5:9.
To find another equivalent ratio, we can look at 10/18 again, then multiply both numbers by the same any number. In this case, let's multiply both numbers by 2. So we now have (10*2)/(18*2) = 20/36 which is the same as 20:36.
We have now found two new ratios equivalent to 10:18.
⇒ 5/9
⇒20/36
Hope this helps,
-Timmeh